Aizu 2249 单源最短路变形 spfa模板改写

http://vjudge.net/contest/view.action?cid=48211#problem/F

Description

King Mercer is the king of ACM kingdom. There are one capital and some cities in his kingdom. Amazingly, there are no roads in the kingdom now. Recently, he planned to construct roads between the capital and the cities, but it turned out that the construction
cost of his plan is much higher than expected.

In order to reduce the cost, he has decided to create a new construction plan by removing some roads from the original plan. However, he believes that a new plan should satisfy the following conditions:

For every pair of cities, there is a route (a set of roads) connecting them.
The minimum distance between the capital and each city does not change from his original plan.
Many plans may meet the conditions above, but King Mercer wants to know the plan with minimum cost. Your task is to write a program which reads his original plan and calculates the cost of a new plan with the minimum cost.

Input

The input consists of several datasets. Each dataset is formatted as follows.

N M

u1v1d1c1

.

.

.
uMvMdMcM

The first line of each dataset begins with two integers, N and M (1 ≤ N ≤ 10000, 0 ≤ M ≤ 20000). N and M indicate the number of cities and the number of roads in the original plan, respectively.

The following M lines describe the road information in the original plan. The i-th line contains four integers, ui, vi, di and ci (1 ≤ ui, vi ≤ N, ui ≠ vi ,
1 ≤ di ≤ 1000, 1 ≤ ci ≤ 1000). ui , vi, di and ci indicate that there is a road which connects ui-th city and vi-th
city, whose length isdi and whose cost needed for construction is ci.

Each road is bidirectional. No two roads connect the same pair of cities. The 1-st city is the capital in the kingdom.

The end of the input is indicated by a line containing two zeros separated by a space. You should not process the line as a dataset.

Output

For each dataset, print the minimum cost of a plan which satisfies the conditions in a line.

Sample Input

3 3
1 2 1 2
2 3 2 1
3 1 3 2
5 5
1 2 2 2
2 3 1 1
1 4 1 1
4 5 1 1
5 3 1 1
5 10
1 2 32 10
1 3 43 43
1 4 12 52
1 5 84 23
2 3 58 42
2 4 86 99
2 5 57 83
3 4 11 32
3 5 75 21
4 5 23 43
5 10
1 2 1 53
1 3 1 65
1 4 1 24
1 5 1 76
2 3 1 19
2 4 1 46
2 5 1 25
3 4 1 13
3 5 1 65
4 5 1 34
0 0

Output for the Sample Input

3
5
137
218

题目大意：有一个王国里有N个城市，国王要从编号为1的城市到达任意城市，启动了一个修路计划在路i和j之间修路长为w，花费c。现在国王要修改一下方案，在原方案中1到达各个城市之间的最短路不变的前提下去掉一些路使得花费最小。
简单思路：这道题其实也是一道最单源最短路的题目。与网络最大流改写为费用流相似，就是在求出最短路的前提下保证花费最少（说白了就是最短路的路径如果有多条相等的时候取花费最小的那个），在spfa算法的松弛操作时加一步花费的判断即可。

#include <stdio.h>
#include <string.h>
#include <queue>
#include <iostream>
#include <algorithm>
using namespace std;
const int maxn=10050;
const int maxe=2005000;
const int INF=1e9;
struct note
{
int to;
int w;
int c;
int next;
};
note edge[maxe];
int head[maxn];
int ip;
void init()
{
memset(head,-1,sizeof(head));
ip=0;
}
void addedge(int u,int v,int w,int c)
{
edge[ip].to=v;
edge[ip].c=c;
edge[ip].w=w;
edge[ip].next=head[u];
head[u]=ip++;
}
int cost[maxn];
int dis[maxn];
bool vis[maxn];
queue<int>q;
void spfa(int s,int n)
{
while(!q.empty())q.pop();
for(int i=1;i<=n;i++)
cost[i]=dis[i]=INF;
memset(vis,false,sizeof(vis));
dis[s]=0;
cost[s]=0;
vis[s]=true;
q.push(s);
while(!q.empty())
{
int u=q.front();
q.pop();
vis[u]=false;
for(int i=head[u];i!=-1;i=edge[i].next)
{
int to=edge[i].to;
int val=edge[i].w;
if(dis[to]>dis[u]+val||(dis[to]==dis[u]+val&&cost[to]>edge[i].c))//有多条最短路时，取花费最小的
{
dis[to]=dis[u]+val;
cost[to]=edge[i].c;
if(!vis[to])
{
q.push(to);
vis[to]=true;
}
}
}
}
}
int main()
{
int n,m;
int u,v,w,c;
while(~scanf("%d%d",&n,&m))
{
if(n==0&&m==0) break;
init();
for(int i=0;i<m;i++)
{
scanf("%d%d%d%d",&u,&v,&c,&w);
addedge(u,v,c,w);
addedge(v,u,c,w);
}
spfa(1,n);
int ans=0;
for(int i=1;i<=n;i++)
ans+=cost[i];
printf("%d\n",ans);
}
return 0;
}